As is generally known, many processes generate waste heat. For example, in electricity generation using steam driven turbines, water is heated in a boiler to create steam which drives a turbine to create electricity. In order to minimize the amount of clean water necessary for this process, the steam must be converted back into water by removing the heat of vaporization, so that the water can be reused in the process. The heat removed from the steam is described as ‘waste heat’ because it is not useful in the production of energy. In another example, in air conditioning systems for large buildings, air inside the building is forced passed coils containing chilled water thereby transferring heat from inside the building into the water. The water is then cooled by the chiller in the evaporator by expansion of a refrigerant from liquid to gas which takes on heat. The warmed refrigerant gas is then compressed and sent to the condenser for cooling and liquefying. Heat is removed from the refrigerant in the condenser. Water cooled condensers transfer the heat rejected from the refrigerant to circulating water. The heated circulating water is in turn sent to the cooling tower where the heat is discharged into the atmosphere. After the refrigerant is liquefied and cooled, the refrigerant is ready to start the cycle anew. Again, this heat is described as waste heat because it is not useful in the refrigeration system and must be removed before the refrigerant is reused in the cooling process.
In both of the foregoing processes, and numerous other processes that require the step of dissipating excess heat, cooling towers have been employed. In wet type cooling towers, water is pumped passed a condenser coil containing the heated steam, refrigerant, or other heated liquid or gas, thereby transferring heat into the water. The warm water is then pumped to the top of the cooling tower and sprayed over a cooling tower fill media to increase the exposed surface area of the warm water and improve heat transfer and evaporation. The fill media is typically comprised of thin sheets of material or splash bars. As the warm water flows down through the fill media, ambient air traverses across the fill media passed the heated water and heat is transmitted from the water to the air by both sensible and evaporative heat transfer. During this process, the flow of air becomes warmer and more humid than the incoming ambient air. The warm, moist air is then forced out of, or exhausted from, the cooling tower and dissipated into the surrounding air. However, for a variety of reasons, it is not desirable to exhaust liquid water, typically in the form of mist or droplets that are called ‘drift’, along with the warm, moist exhaust air. For example, drift represents a loss of circulating water. In another example, in some atmospheric conditions, the drift may freeze on and adversely affect the operation of the components in the cooling tower or other nearby machines and structures.
While other steps can be taken to reduce the amount of drift from cooling towers, these steps are often insufficient and cause other problems. For example, slowing the speed of the flow of air may reduce drift but the tradeoff is increasing the volume of the fill media along with the size of the cooling tower. Placing a maze of baffles between the fill media and the cooling tower exhaust may also reduce drift. Unfortunately, the baffle may increase static pressure across the fill media requiring more powerful fans to draw the air through the cooling tower.
Accordingly, there is a need for reducing drift in cooling towers to address the problems described above and/or problems posed by other conventional approaches.